Average Butt Size — What the Data Actually Shows

The Short Answer Most Sites Won't Give You

If you've ever Googled "average butt size," you've probably found a mess of unsourced claims, clickbait headlines, and numbers pulled from thin air. The reality is more nuanced — and more interesting — than a single number.

Anthropometric research (the scientific measurement of the human body) gives us real data on hip circumference, gluteal fold dimensions, and regional fat distribution. But "butt size" isn't a single measurement, and averages shift dramatically depending on sex, ethnicity, age, and body composition.

Here's what the peer-reviewed literature actually tells us.

What Researchers Measure (and Why It Matters)

Clinical studies don't measure "butt size" the way you might imagine. Instead, researchers rely on standardised anthropometric landmarks:

Hip circumference is the most commonly reported measurement. It's taken at the widest point of the buttocks, with the tape measure parallel to the floor. This captures overall lower-body width, including both gluteal muscle mass and subcutaneous fat.

Gluteal fold depth and projection measure how far the buttocks extend posteriorly from the sacrum. These are less commonly reported in large population studies but are standard in plastic surgery research.

Waist-to-hip ratio (WHR) contextualises butt size relative to the waist, and is one of the most studied metrics in body composition research.

Average Hip Circumference by Sex

The most robust population-level data comes from national health surveys, particularly the U.S. National Health and Nutrition Examination Survey (NHANES) and the UK National Sizing Survey.

Women (ages 20–59)

• United States: The mean hip circumference is approximately 104–107 cm (41–42 inches), based on NHANES data. This has increased by roughly 3 cm over the past two decades, tracking alongside rising average BMI.
• United Kingdom: The mean sits slightly lower at around 102–104 cm (40–41 inches).
• East Asia: Studies from Japan and South Korea report averages in the range of 91–95 cm (36–37 inches), reflecting different body composition patterns and lower average BMI.

Men (ages 20–59)

• United States: The mean hip circumference is around 102–104 cm (40–41 inches).
• United Kingdom: Approximately 100–103 cm (39–41 inches).
• East Asia: Around 92–96 cm (36–38 inches).

These numbers carry enormous standard deviations — typically ±8–12 cm — which means the "normal" range is far wider than most people realise.

Why Averages Are Misleading

Quoting a single average is tempting but problematic for several reasons.

Body composition matters more than circumference. Two people with identical hip measurements can look dramatically different if one carries more muscle and the other carries more fat. A hip circumference of 105 cm on a 5'2" woman looks completely different from the same measurement on someone who is 5'10".

Ethnicity and genetics play a significant role. Research consistently shows that women of West African descent tend to carry proportionally more gluteal fat and muscle mass than women of East Asian or Northern European descent, even at the same BMI. A 2016 study in the American Journal of Human Biology found that gluteal fat distribution varies by up to 22% between ethnic groups at identical body fat percentages.

Age changes everything. Gluteal volume tends to peak in the late 20s to early 30s, then gradually decreases as both muscle mass and subcutaneous fat redistribute. By age 60, average gluteal projection can decrease by 15–20% compared to age 30, primarily due to sarcopenia (age-related muscle loss) and gravitational fat redistribution.

Butt Size Trends Over Time

Average hip circumference has been rising across most developed nations, consistent with increases in average BMI. NHANES data shows that the mean female hip circumference in the U.S. increased from approximately 100 cm in 1988 to about 107 cm by 2018.

But body composition has shifted too. Advances in fitness culture, particularly the rise of glute-focused training, mean that a larger proportion of younger women carry more gluteal muscle mass than previous generations. The cultural shift toward muscular, rounded glutes — rather than simply slim figures — has had a measurable impact on the population-level data, at least in demographics that participate heavily in resistance training.

What About Gluteal Projection?

Hip circumference captures width, but it doesn't tell you much about how far the buttocks project — which is what most people actually mean when they talk about "butt size."

Gluteal projection is harder to measure in population studies, so the data is thinner. Plastic surgery literature provides the most detailed numbers, though these are based on clinical populations (people seeking procedures) rather than the general public.

Studies from the Aesthetic Surgery Journal report average gluteal projection of approximately 5–7 cm in women and 3–5 cm in men, measured as the perpendicular distance from the sacral plane to the point of maximum posterior extension. Post-BBL patients typically show projections of 7–10 cm.

How to Think About Your Own Measurements

Rather than fixating on whether you're "above or below average," the more useful approach is to understand your own proportions:

Waist-to-hip ratio is a better indicator of aesthetic proportion than raw hip circumference. Research on attractiveness perception consistently identifies a WHR of approximately 0.67–0.72 in women and 0.85–0.90 in men as perceived as most attractive across cultures — though these preferences do vary.

Frame-relative size matters. Your hip circumference relative to your shoulder width, height, and ribcage circumference determines how your proportions read visually. An "average" hip measurement on a petite frame creates a very different silhouette than the same measurement on a tall, broad-shouldered build.

The Bottom Line

The average hip circumference for adult women in the U.S. is around 104–107 cm (41–42 in), and for men around 102–104 cm (40–41 in). But these numbers vary enormously by ethnicity, age, body composition, and geographic region.

More importantly, "average" doesn't mean "normal" or "ideal." The standard deviation on these measurements is large enough that the vast majority of people fall within the normal range — even if they feel like outliers.

Curious where you fall? RateMyAss.ai gives you a data-driven comparison.